how to "test" intake air temp sensor?? - PeachParts Mercedes-Benz Forum

byronj · #1 02-19-2011, 02:09 PM

1995 e320..diagnostic module gives code #9 intake air temperature sensor, open circuit.....question...should the sensor have continuity ?? thanks...byronj

oldsinner111 · #2 02-20-2011, 08:25 AM

current should pass thru it.It takes 12 volts to operate.

mpolli · #3 02-20-2011, 01:47 PM

I think it should measure some resistance. If you have an OBDII plug, some scanners will read the air temp sensor. But I don't know if the 95 had OBDII yet.

JohnM. · #4 02-20-2011, 05:03 PM

Does anyone know what exactly the air intake temperature controls? The early W124s had no AIT in the air boot. When I read my codes, it also said mine was bad too. But the car runs great.

mpolli · #5 02-20-2011, 05:46 PM

It's for the EFI system.

JohnM. · #6 02-20-2011, 11:50 PM

Quote:

Originally Posted by mpolli

It's for the EFI system.

Obviously. But what EXACTLY does it control/influence in the FI system?

Pili380SL · #7 02-22-2011, 02:17 PM

I would think that since warmer air is less dense, the air intake tamp sensor probably adjusts the perameters for the MAF, basically "warning" the MAF of the density of the incoming air, allowing the system to adjust quicker. Just a guess.

oldsinner111 · #8 02-22-2011, 02:28 PM

air intake sensor with oxygen sensor controls lean or rich mixture.Thats like my chip fools air intake sensor to read perfect temps,so mixture will be at perfect 14.7 to 1.
I now before my chip in cold winter below 25 degrees my mileage suffered.Now its stable on cold days as warm days.

mbdoc · #9 02-22-2011, 02:56 PM

With Ohm meter on the sensor connections, here are the readings

Pili380SL · #10 02-22-2011, 03:26 PM

Thanks mbdoc! I'll check mine tonight.

rayhennig · #11 02-23-2011, 03:46 AM

Quote:

Originally Posted by Pili380SL

Thanks mbdoc! I'll check mine tonight.

I got my genuine MB temp sensor for €12 and installed it in 30 secs. My old one was open circuit so I knew it was dead.

New one made hot starts a lot smoother.

This was on a 300-24 so it's the mechanical KE Jetronic not the integrated system you have.

RayH

Pili380SL · #12 02-23-2011, 09:55 AM

This morning, a cool morning it was probably 35° max in my garage the sensor measured 2910Ω so it thought it was about 100°F. Mine's been running a little rich it seems; shouldn't the incorrect sensor calibration cause a lean condition since it thought the air was warmer? Regardless, I ordered one this morning.

EDIT: After rereading, I realized mbdoc's chart was for a M104 engine, and it shows a different part number than on the M119. Since the original incident, the car seems to be improving each time I run it. Last night I drove it for about half an hour and the only thing I could detect at the end was a slight variance in RPM sitting in park. Whatever the issue is, it seems to be taking care of itself, which is not great for the confidence of driving it lol.